1. Field of the Invention
This invention relates to a liquid tank, more particularly to a liquid tank installed in the refrigeration cycle of an air-conditioning system.
2. Background Art
The general purpose of the liquid tank (receiver/drier) of an air-conditioning system is to temporarily store refrigerant from the condenser and to effect air-liquid separation and removal of water from the refrigerant. In recent years, various innovations have been directed to reducing the diameter of the liquid tank so as to incorporate it in, or make it a subassembly of, the condenser.
An example of this is seen in the conventional liquid tank 1 shown schematically in the vertical sectional view of FIG. 14. This liquid tank 1 has a tank body 2, a head section 3 of flat type, desiccant 4 and a refrigerant takeoff tube 5.
The tank body 2, which is a slender cylinder tapered downward and closed at the bottom, is configured to hold the desiccant 4 at its middle section and refrigerant R at its bottom section.
The head section 3 closes the upper opening of the tank body 2 and is formed with a refrigerant inlet port 6 and a refrigerant outlet port 7. The refrigerant inlet port 6 can be connected to an outlet side tank 9 of a condenser 8 and the refrigerant outlet port 7 to the evaporator 11 side through an expansion valve 10.
The desiccant 4 absorbs and removes water entrained by the refrigerant R. The refrigerant R passes through the desiccant 4 and is pooled in the bottom section of the tank body 2, from where it passes out of the liquid tank 1 (in the direction of the expansion valve 10 and the evaporator 11) through the coolant takeoff tube 5.
In the liquid tank 1 of this configuration, the head section 3 is formed to a smaller diameter and greater height than in earlier liquid tanks of this type and is mounted on the outlet side tank 9 of the condenser 8 by a bolt 12. This structure does not differ greatly from that of earlier liquid tanks and provides only limited cost merit.
FIG. 15 is a vertical sectional view schematically showing another conventional liquid tank. The liquid tank 13 shown here has its refrigerant inlet port 6 at the upper portion of the tank body 2 and its refrigerant outlet port 7 at the lower portion thereof. The refrigerant R flows straight through the tank body 2 from the refrigerant inlet port 6 to the refrigerant outlet port 7.
The cost of the liquid tank 13 is increased by the need to form the refrigerant inlet port 6 and the refrigerant outlet port 7 at separate portions. Moreover, since the refrigerant inlet port 6 and the refrigerant outlet port 7 are widely separated, an attempt to mount the liquid tank 13 directly on the condenser 8 encounters problems when, for example, a condenser 8 utilizing the subcooling structure is adopted, because it becomes difficult to secure the required pitch of the connection portions at the inlet and outlet for returning the refrigerant R to the condenser 8.
FIG. 16 is a vertical sectional view schematically showing still another conventional liquid tank. The liquid tank 14 shown here has both the refrigerant inlet port 6 and the refrigerant outlet port 7 provided at the lower portion of the tank body 2 and is directly mounted on the outlet side tank 9 of the condenser 8.
Since the refrigerant inlet port 6 and the refrigerant outlet port 7 of the liquid tank 14 are formed close to each other, the air-liquid capability of the liquid tank 14 becomes insufficient when the flow rate of the refrigerant R from the condenser 8 into the liquid tank 14 is fast.
Liquid tanks are also taught by, for example, Japanese Patent Disclosures Hei 2-267478, Hei 4-103973, Hei 5-66074 and Hei 8-183325.
A conventional liquid tank of another type will now be briefly explained with reference to FIGS. 17 and 18.
The liquid tank 15 shown in a partially cut-away sectional view in FIG. 17 and in plan view in FIG. 18 has a tank body 2, a flat type head section 3, desiccant 4 and a coolant takeoff tube 5.
The tank body 2, which is a slender cylinder tapered downward and closed at the bottom, is configured to hold the desiccant 4 at its middle section and pool refrigerant R at its bottom section.
The head section 3, which closes the upper opening of the tank body 2, is formed with a refrigerant inlet port 6, a refrigerant outlet port 7 and a center hole 17 fit with a transparent sight glass 16 to enable visual observation of the interior. As shown in FIG. 18, it is also provided with a pressure switch 18 and a fusible plug 19.
An inlet side connector flange 20 is provided at the refrigerant inlet port 6 and an outlet side connector flange 21 at the refrigerant outlet port 7 to enable introduction and extraction of the refrigerant.
The desiccant 4 absorbs and removes water entrained by the refrigerant R. The refrigerant R passes through the desiccant 4 and is pooled in the bottom section of the tank body 2, from where it passes out of the liquid tank 15 through the coolant takeoff tube 5.
Specifically, the coolant takeoff tube 5 is disposed along the axis of the liquid tank 15 and connected with the center hole 17 of the head section 3, from where it communicates with the refrigerant outlet port 7 through a lateral communicating hole 22 of the head section 3.
The outer end of the lateral communicating hole 22 is stopped with a bull plug 23.
The productivity of the liquid tank 15 is lowered by the need to machine the lateral communicating hole 22. An attempt has therefore been made to lower both material cost and machining cost by, as shown in the liquid tank 24 of FIG. 19, omitting the sight glass 16 and disposing the refrigerant outlet port 7 directly above the coolant takeoff tube 5, thereby eliminating the need to machine the lateral communicating hole 22.
In this case, however, functional and assembly considerations require installation of the coolant takeoff tube 5 at the center of the tank body 2. The location of the refrigerant outlet port 7 is therefore also limited to the center of the tank body 2 and, accordingly, to the center of the head section 3.
Locating the refrigerant outlet port 7 at the center of the head section 3 is disadvantageous, however, since it restricts the layout of the various other aforesaid components and holes that have to be mounted on or formed in the head section 3 and, as such, lowers the efficiency of the assembly and tube installation work. In the worst case, it may be impossible to find a workable layout and the idea of positioning the refrigerant outlet port 7 at the center will itself have to be abandoned.
Liquid tanks of this type are taught by, for example, Japanese Utility Model Disclosures Hei 3-27573 and Hei 6-14870.
Additional problems related to the conventional liquid tank 15 will now be explained with reference to FIGS. 20 to 23. FIG. 20 is a schematic plan view of the liquid tank 15 similar to FIG. 18, and FIG. 21 is a vertical sectional view thereof similar to FIG. 17.
As already pointed out, the liquid tank 15 has the problem of poor productivity owing to the need to machine the lateral communicating hole 22.
The liquid tank 24 shown in FIG. 22 and FIG. 23 (similar to FIG. 19) represents an attempt to overcome this problem by omitting the sight glass 16 and disposing the refrigerant outlet port 7 directly above the coolant takeoff tube 5, thereby eliminating the need to machine the lateral communicating hole 22 while also lowering material cost and machining cost.
In this case, however, functional and assembly considerations require installation of the coolant takeoff tube 5 at the center of the tank body 2. The location of the refrigerant outlet port 7 is therefore also limited to the center of the tank body 2 and, accordingly, to the center of the head section 3.
Locating the refrigerant outlet port 7 at the center of the head section 3 positions the refrigerant outlet port 7 near the refrigerant inlet port 6 and this location of both the refrigerant inlet port 6 and the refrigerant outlet port 7 toward one side of the head section 3 restricts the layout of the various other components and holes that have to be mounted on or formed in the head section 3 and, as such, lowers the efficiency of the assembly and tube installation work. In the worst case, it may be impossible to find a workable layout and the idea of positioning the refrigerant outlet port 7 at the center will itself have to be abandoned.
Liquid tanks of this type are taught by, for example, Japanese Patent Disclosures Sho 61-195256 and Hei 2-71067.
This invention was accomplished in light of the foregoing problems. One object of a first aspect of the invention is to provide a liquid tank that is of the type of the liquid tank 14 shown in FIG. 16 but that has excellent air-liquid separation capability.
Another object of the first aspect of the invention is to provide a liquid tank that is both easy to assemble and high in cost merit.
Another object of the first aspect of the invention is to provide a liquid tank that is of simple structure and excellent in mountability on a condenser.
Another object of the first aspect of the invention is to provide a liquid tank whose mountability on a condenser which utilizes a subcooling structure is excellent in terms of ease of returning refrigerant to the condenser.
One object of a second aspect of the invention is to provide a liquid tank that enables the refrigerant outlet port to be positioned at the center of the head section with minimal cost increase.
Another object of the second aspect of the invention is to provide a liquid tank that facilitates the layout of components at the head section by providing a degree of freedom in selecting the refrigerant outlet port machining position.
Another object of the second aspect of the invention is to provide a liquid tank that is excellent in assembly and fabrication property.
One object of a third aspect of the invention is to provide a liquid tank that enables the refrigerant outlet port to be positioned at the center of the head section with minimal cost increase.
Another object of the third aspect of the invention is to provide a liquid tank that enhances the freedom of laying out tubes and other components connected to the head section.
Another object of the third aspect of the invention is to provide a liquid tank that is excellent in assembly and fabrication property.